This research will test the postulate that the lecithin: cholesterol acyltransferase reaction plays a role in the transport of dietary lipid as well as in the removal of cholesterol from peripheral cells. Specific experiments will study the reaction's role in recycling the apolipoproteins and unesterified cholesterol of chylomicrons. In vitro experiments, performed with the plasma lipoproteins of patients with familial LCAT deficiency, will study the reaction's effects on the transfer of apolipoproteins and cholesteryl ester. Cell culture experiments with human fibroblasts, endothelial cells, and smooth muscle cells will study the reaction's effects on removal of cellular cholesterol. Finally, in vivo and in vitro experiments with nonhuman primates will study the mechanisms that regulate the uptake of high density lipoproteins by the intestine and liver.